Specification Part 3 - Road & Bridge Works - Urban Administration ...

(ii) Separately as 25 mm nominal single size, 12.5 mm nominal size graded aggregates and Tine
aggregate of crushed stone dust or sand or a combination of these two.
The material after blending shall conform to the grading as indicated in Table 600-1.
TABLE 600-1. AGGREGATE GRADATION FOR DRY LEAN CONCRETE
Sieve Designation
26.50 mm
19.00 mm
9.50 mm
4.75 mm
600.00 micron
75.00 micron
Percentage passing the sieve by weight
100
80-100
55-75
35-60
10-35
0-8
601.2.4. Water: Water used for mixing and curing of concrete shall be clean and free from
injurious amounts of oil, salt, acid, vegetable matter or other substances harmful to the finished
concrete. It shall meet the requirements stipulated in IS : 456.
601.2.5. Storage of materials: All materials shall be stored in accordance with the provisions of
Clause 1014 of these Specifications and other relevant IS Specifications. All efforts must be
made to store the materials in proper places so as to prevent their deterioration or contamination
by foreign matter and to ensure their satisfactory quality and fitness for use in the work. The
storage place must also permit easy inspection, removal and storage of materials. All such
materials even though stored in approved godowns must be subjected to acceptance lest
immediately prior to their use. The requirement of storage yard specified in Clause 602.2.9 shall
also be applicable.
601.3. Proportioning of Materials for the Mix
601.3.1. The mix shall be proportioned with a maximum aggregate cement ratio of 15: 1. The
waiter content shall be adjusted to the optimum as per Clause 601.3.2 for facilitating compaction
by rolling. The strength and density requirements of concrete shall be determined in accordance
with Clause 601.6 by making trial mixes.
601.3.2. Moisture content: The right amount of water for the lean concrete in the main work shall
be decided so as to ensure full compaction under rolling and shall be assessed at the time of
rolling the trial length. Too much water will cause the lean concrete to be heaving up before the
wheels and picked up on the wheels of the roller and too little will lead to inadequate compaction,
a low in-situ strength and an open-textured surface.
The optimum water content shall be determined and demonstrated by rolling during trial length
construction and the optimum moisture content and degree of compaction shall be got approved
from the Engineer. While laying in the main work, the lean concrete shall have a moisture content
between the optimum and optimum +2 per cent, keeping in view the effectiveness of compaction
achieved and to compensate for evaporation losses.
601.3.3. Cement content: The minimum cement content in the lean concrete shall not be less
than 150 kg/cu.m. of concrete. If this minimum cement content is not sufficient to produce
concrete of UK specified strength, it shall be increased as necessary without additional cost
compensation to the Contractor.
601.3.4. Concrete strength: The average compressive strength of each consecutive group of 5
cubes made in accordance with Clause 903.5.1.1 shall not be less than 10 MPa at 7 days. In
addition, the minimum compressive strength of any individual cube shall not be less than 7.5 MPa
at 7 days. The design mix complying with the above Clauses shall be got approved from the
Engineer and demonstrated in the trial length construction.